1. Field of the Invention
This invention relates in general to the cleaning and treatment of wellbores and well formations and more particularly to such treatment for inhibiting and removing accumulations of paraffin.
2. Description of the Prior Art
During the production of petroleum or gas from a subterranean formation through a wellbore leading to the surface, one difficulty encountered is the accumulation of paraffin and heavy hydrocarbons within the wellbore. These accumulations most frequently occur at the producing formation and within the production tubing. The paraffin accumulations reduce the size of the passageways through which the oil or gas is produced so that the amount of oil or gas produced is restricted.
Various mechanical, thermal and chemical methods of treating wellbores for inhibiting and removing accumulations of paraffin have been utilized. Mechanical methods generally consist of scrapers which are moved through the wellbore to scrape the deposits from the tubing. Thermal methods comprise circulating hot oil or water through the wellbore to melt or increase the solubility of the paraffin deposits. The chemical methods comprise circulating solvents and wax crystal modifiers or paraffin dispersants through the wellbore.
A particular problem with the mechanical and thermal methods of removing paraffin deposits is that they are relatively expensive and require the well to be taken out of service during the treatment process.
Chemical methods for treating wellbores to inhibit and remove paraffin have also not been entirely satisfactory. Most importantly, some of the chemical solvents and dispersants can harm the producing formation by chemically changing the wettability of the formation or by reacting with the formation to form insoluble deposits which clog the formation. Moreover, some chemical treatments must be carefully tailored to suit the particular crude or paraffin with which they will be used.